An ingredient capsule contains food ingredients or substances that are used by addition of a liquid for preparing a beverage or, to a larger extent, liquid comestibles.
A beverage preparation machine comprises a receptacle for accommodating a capsule and a fluid injection system for injecting a fluid, preferably a liquid such as water, under pressure into said capsule. For instance, water injected under pressure in the capsule, for the preparation of a coffee beverage, is preferably hot, that is to say at a temperature above 70° C. However, in some particular instances, water might also be at ambient temperature. The pressure inside the capsule during extraction and/or dissolution of the capsule ingredient(s) is typically about 1 to 6 bar for dissolution products, and 2 to 12 bar for extraction of roasted and grounded coffee. Such a preparation process greatly differs from the so-called “brewing” process of beverage preparation—particularly for tea and coffee, in that brewing requires a long time of infusion of the ingredient(s) by a fluid (e.g. hot water), whereas the beverage preparation process allows a consumer to prepare a beverage, for example coffee, within a few seconds.
The principle of extracting and/or dissolving the ingredient(s) of a closed capsule under pressure is known and consists typically of inserting the capsule into a receptacle of a machine, injecting a quantity of pressurized water into the capsule, so as to create a pressurized environment inside the capsule either to extract the ingredient(s) or dissolve it, and then release the extracted ingredient(s) or the dissolved ingredient(s) through the capsule. Capsules of this type have already been described for example in the Applicant's European patents 1 472 156 B1, and 1 784 344 B1.
Machines operating in accordance with this principle have already been described for example in documents CH 605 293 and EP 242 556. According to these documents, a beverage preparation machine comprises a receptacle for accommodating a capsule and a piercing and injection element made in the form of a hollow needle comprising in its distal region one or more liquid injection orifices. The hollow needle has a dual function in that it pierces and therefore opens the top portion of the capsule on the one hand, and forms through inlet channel inside the needle enabling water to flow through to the distal region the capsule for being injected thereinto on the other hand.
When the beverage to be prepared is coffee, a capsule may contain roast and ground coffee powder as an ingredient, which is to be extracted thanks to hot water injected therein.
Capsules have been developed for such an application, which are disclosed in the Applicant's European patent EP 1 784 344 B1, and European patent application EP 2 062 831.
In short, a capsule of this type typically comprises:                a hollow body and an injection wall which is impermeable to liquids and to air and which is attached to the body at the top end of the capsule and adapted to be punctured by e.g. an injection needle of the machine;        a chamber containing a bed of roast and ground coffee to be extracted;        an aluminium membrane disposed at the bottom end of the capsule for closing said capsule and maintaining the internal pressure within the chamber, said membrane being associated with perforating means for forming dispensing holes in the membrane when said internal pressure within the chamber reaches a certain predetermined value,        optionally, means configured to break the jet of water so as to reduce the speed of the jet of water injected into the capsule and distribute water across the bed of substance at a reduced speed.        
As the beverage preparation machine of the above-described kind uses water as extraction fluid scaling deposits are formed in the parts of the machine which are in contact with water that is the water circulation system.
These scaling deposits get accumulated in the parts of the water circulation system over time along with the use of the machine.
This may lead through inlet channel of the needle that is used for injecting water into the pierced capsule to be clogged with time.
Users of these machines are asked to regularly clean the water circulation system with a descaling or anti-scaling product in order to avoid clogging of the system and in particular of the needle.
However, as the diameter of the channel internal to the needle is narrow it is particularly favourable to scaling.
In order to deal with this problem the existing machines are equipped with a cleaning tool which takes the form of a pin-shaped member.
This pin-shaped member has an outside diameter which corresponds to the internal diameter of the needle channel taking account of the mechanical tolerance.
Machines' user guide provides consumers with instructions as to how regularly use this cleaning tool in order to avoid scaling and therefore subsequent clogging of the machines.
Users are instructed to introduce the pin-shaped member into the needle channel by an end thereof (the end by which water is supplied to the channel) through the opposite end in order to rub the inner wall of the channel and therefore remove any scaling deposits.
Although technically satisfactory, such a manual operation requires the user to regularly plan the cleaning, which is not satisfactory. Furthermore, in case the user omits the regular descaling maintenance, this may result in clogging of the needle, such that it then necessitates to send the machine to an after-sales service, which is of course undesirable.